An idea that might be worth considering. In any 2/1 GF sequence where trumps have not yet been agreed but both major strains are possible, a 2NT call forces one-under calls by the other person, with 3C as a minor flag.
An example from BBF is 1S-2minor, 2S-2NT, ? At this point, Opener rebidding 3C to agree Responder's minor, 3D for hearts (6-4 weakish), or 3H to rebid spades allows three-level agreement of all suits, which solves some problems.
Similarly, 1S-2H, 2S-2NT is a good start for this.
If only one major strain is possible, but both minors are possible, then bidding the minor naturally but always 3H for whichever major (and 3S as a confirm call) makes sense. E.g., 1M-2C, 2D-2NT, ?
If all four suit strains are actually possible, one-under still might make sense, with 3S for clubs. This hurts in club sequences but helps in all others.